Many of the objects in everyday use contain substances which become an objectionable potential pollutant due to continuous or intermittent release into the environment. They may be synthetic substances, such as plastics, synthetic resins or preservatives, or natural substances, such as mordants, oils or biocides. Of particular significance are the chemical compounds which occur either as gases, vapors, or in the solid form and may be bound by sorption on coarse or fine dusts, especially those environmental chemicals which increasingly occur as a pollutant load in the outdoor or indoor air of humans and animals. These are, e.g., formaldehyde, pentachlorophenol or pyrethroid pesticides, which may occur especially in furnishings of buildings and interior spaces, or in textile materials.
Objects, e.g., wooden components in structures or building structures, such as beams, ornaments, panelings, etc., as well as wooden objects and textiles, e.g., leather covers, are frequently inaccessible to a direct analysis, because they are too large, too bulky, or too costly. Even if the analysis of these objects is possible, it is usually very expensive or difficult with respect to the emission of pollutants. In this case, it is necessary to take samples of the objects, and the samples are then tested irreversible destructively, i.e., the so-called substance samples are subjected to a consuming chemical or physical processing, i.e., destruction, in the course of the analysis, and they cannot be returned to the place from where they were taken. Furthermore, only the pollutant potential can be determined by such a consuming analysis. Data on the actual release of the potentially harmful substances into the environment can be obtained only indirectly at best.
In contrast, hundreds of organic compounds, which are frequently of anthropogenic origin, can be detected in the atmosphere, besides the inorganic compounds (CO, NO.sub.x, SO.sub.2, etc.), which occur at even higher concentrations (cf. I. L. Marr, M. S. Cresser, L. J. Ottendorfer: Analytische Chemie fur die Praxis: Umweltanalytik Analytical Chemistry for Practice: Environmental Analysis!, Georg Thieme Verlag, Stuttgart, 1988). The following methods have been known from the state of the art for enriching these organic constituents of air, which usually occur at low concentrations in the form of gases, vapors and/or aerosols:
1. Physical or chemical adsorption in liquids, PA1 2. Condensation at low temperatures (freezing out), and PA1 3. Adsorption on solids.
One major drawback of the adsorption method is that the organic constituents of air, which occur in trace concentrations, can be quantified only inaccurately in the liquid adsorbents. Losses, which distort the result, are unavoidable during concentration.
Condensation is suitable predominantly only for especially high mass concentrations and components having a relatively high vapor pressure. It is disadvantageous here that the water vapor present is also condensed and may interfere with the subsequent chemical analysis.
In contrast, various practical methods of adsorptive enrichment have proved to be successful. However, a direct analysis is not possible in this case, either, because elution or thermal desorption of the analytes collected is inevitable in most cases before the analysis proper. The chemical and physical properties of the various adsorbents lead to a less stable retention of the lower-boiling constituents of air, i.e., to an earlier breakthrough of the compounds through the layer of adsorbent, as a consequence of which a quantitative determination will become uncertain (cf. K. Figge, W. Rabel, and A. Wieck: Adsorbents for the Enrichment of Organic Constituents of Air, Fresenius Z. Anal. Chem., Vol. 327 (1987), pp. 251-278).
To obtain data on the concentration in the evaluation of an analysis, the substance to be measured must be brought to the adsorbent in a defined manner during the enrichment. Sampling methods for enriching substance emissions released from objects emitting pollutants when the substance admissions are fed to an adsorption layer by defusing or penetration and are enriched in the adsorption layer by adsorption have been known from, e.g., Drager-Rohrchen Handbuch: Boden-, Wasser-und Luftuntersuchung sowie technische Gasanalyse Drager Tube Handbook: Soil, Water, and Air Analyses as well as Industrial Gas Analysis!, 8th edition, Lubeck, 1991.
Systems with so-called active sampling and passive sampling methods are distinguished. The enriched air volume is the decisive reference quantity for the subsequent calculation of the concentration in the active system. Passive systems are designed, in general, for sampling over longer periods of time and for determining average concentrations or shift mean values. In contrast, the instantaneous environmental concentration is determined in the case of an active sampling. However, both methods fail to furnish any information on or are not directly related to the actual source emitting or releasing the pollutant, but they are sensitive to the room air only.
Processes and devices for collecting gases, especially formaldehyde, by sorption for enriching substance emissions released from objects emitting pollutants when the substance admissions are fed to an adsorption layer by defusing or penetration and are enriched in the adsorption layer by adsorption have been known from DE-A-38 42 607 and DE-A-40 25 842. However, these processes are also limited to the adsorption of gases present in the room air. Object-related sampling cannot be performed.